The server error comes in many forms. Here are some of the most common ones:
550 Relaying denied
550 Relay not permitted
550 Relaying not allowed
550 5.7.1 Unable to Relay
550 5.7.1 <email@example.com>... Relaying denied
553 SMTP Relaying Denied
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
554 <firstname.lastname@example.org>: Relay access denied
Mail servers will not relay mail from just anyone. Otherwise, spammers could flood the mail server, making it do their dirty work. You must be authorized to use a mail server for relaying. Unauthorized users will always receive the "Relaying Denied" error.
- By far the most common cause is that no user name and password were specified. In Gammadyne Mailer, these fields are on the Servers/SMTP branch under "SMTP Authentication". The user/password is often the same as for your email account, although sometimes the SMTP server has separate credentials. If authentication is failing, you will need to contact the SMTP server's administrator.
- This error can sometimes be circumvented by first checking for incoming email. Some servers are smart enough to recognize that when you are properly authenticated to receive mail, then you should also be able to send mail.
- Sometimes the Sender of the email is required to be a user on the server. The Sender is where bounce-backs are sent when the email is undeliverable (it appears in the "MAIL FROM" SMTP command). Most email programs always use the From: or Reply-To: header for the sender, and do not allow it to be specified. In Gammadyne Mailer, it can be changed with the "Sender:" field on the "Headers" branch.
- The "From:" header may need to be a user that is local to the SMTP server. If the server is really restrictive, the From: header may need to be identical to the SMTP user name. In other words, if you are logging on to the SMTP server with the email@example.com account, then the From: header needs to be firstname.lastname@example.org
- If the mail server is on a Local Area Network, it may be necessary to specify the mail server's local IP address, not its name.
- If the mail server belongs to your ISP, it is possible that the mail server will only relay mail for users that are currently connected to the ISP. If you want to be able to send mail when using a different connection, you will need to ask your ISP if "SMTP authenticated login" is supported. If it is, they will give you a user name and password. In Gammadyne Mailer, this must be entered on the Servers/SMTP branch under "SMTP Authentication".
- Occasionally, a mail server may require that the email program say hello properly. This corresponds to the HELO/EHLO command in the SMTP protocol. The mail server may require that this command reports a proper domain name that is authorized to send email. Even though this practice is discouraged, some mail servers perform this check as a form of spam prevention. In Gammadyne Mailer, this corresponds to the "Override EHLO Domain" field on the Send/Delivery branch (uncheck "Hide Advanced Settings" on the Options menu first).
450 Relaying temporarily denied. Cannot resolve PTR record for 18.104.22.168
550 5.7.1 <email@example.com>... Relaying denied. IP name lookup failed [22.214.171.124]
550 Relaying denied. IP name possibly forged